This invention relates to a system for performing an assay of slide mounted biological cell samples, and more particularly, for providing an automated method and arrangement to identify to the system locations at which to perform selected analysis functions.
The diagnosis and/or prognosis of a patient's condition frequently includes the removal of a cell sample, such as a tissue mass, from the patient. Although an attending physician may have good intuition regarding the patient's diagnosis and/or prognosis, confirmation of the diagnosis with histological examination of the cell sample removed from the patient is necessary. The histological examination entails cell staining procedures which allow the morphological features of the cells to be seen relatively easily in a light microscope. A pathologist, after examining the stained cell sample, makes a qualitative determination of the state of the tissue and reaches a conclusion regarding the prognosis for the patient. While this diagnostic method has a long history, it is somewhat lacking in scientific rigor since it is heavily reliant on the subjective judgment of the pathologist and it is extremely time-consuming.
The alternative to the strictly qualitative and time-consuming human analysis is automated cell analysis where the pathologist uses specialized equipment to perform the analysis. Flow cytometry equipment is one type of automated apparatus for cell analysis. With flow cytometry, mass tests are performed in gross on a specimen cell population without a researcher being able to exclude or include certain data of the population. The specimen is measured "as is" without really knowing what cells are being measured and how many. Important single cell data or data from relatively small groups of cells are lost in the overall averaging of a specimen. Further, relatively large amounts of a specimen have to be used to provide a required level of accuracy. Again, small changes in individual cells or small cell populations cannot be discerned.
Commercially available general purpose flow cytometers are very expensive and can handle only liquid blood specimens or tissue disaggregated specimens. Additionally, flow cytometers are incapable of working on standard tissue sections or using conventional microscope slides which are the preferred specimen forms of pathology laboratories.
Although the automation of cell analysis using microscope slide cell samples is exceedingly difficult, such has been automated to a human-machine interactive level. One such method and apparatus is described in U.S. Pat. No. 4,471,043 to Bacus, for Method And Apparatus For Image Analysis of Biological Specimens. Cell samples are attached to slides and an operator adjusts the system optics to view desired image fields of the cell sample. The operator then selects and classifies particular cell objects of the sample. After such operator action, the automated equipment quantitatively measures particular attributes of the selected and classified cell objects and records a digital representation of the optical image. The measured attributes can be reported on a per object basis or on an accumulated basis, and the stored image representations can later be read form memory for review.
Heretofore, slides prepared for use in image analysis often have different areas widely spaced on the slide at which different actions or functions are to be performed. For instance, a slide may have a clear area thereon which is selected for use in adjusting or calibrating the light and color levels needed for analysis of specimens located on the slide in another area of the slide. The operator may want to adjust the light level for each slide or for a group of slides in a slide tray or carrier. Also, the specimen cells may be located in a small portion of a specimen area on the slide and considerable time would be saved if the carrier positioned the slide specimen with this small portion of specimens directly beneath the microscope rather than having to examine large empty areas before locating the small specimen. Likewise, a calibration specimen in a calibration area may take a long time to locate by the machine because of the large empty area about the specimen. Still in other slides such as blood slides, the blood sample may cover the entire slide leaving no clear area for light setting.
The slides can be searched by the analysis apparatus to find particular areas, such as specimen or calibrate areas, however, doing so with a for example, 40.times. objective used for analysis, is difficult and time-consuming. The image area of a high power objective is only on the order of 20 by 20 microns so that each step in a search routine is very short and many such steps must be performed. Further, the depth of field with a high power objective is very short and refocusing must occur at each image field. When a clear area is under the slide, as will be the case for most of a search for small samples, much time is wasted trying to focus on non-existent objects. It is a significant problem in an automated analysis to be able to locate a small area or a specimen on a slide and to perform a desired function on each of a plurality of areas on the slides in a carrier in a fast and efficient manner.